1. Field of the Invention
The field of the invention is a control system for a high pressure liquid spraying system.
2. Description of the Prior Art
In recent years the use of a high pressure water spray, 500 to 20,000 psi, for removing or cleaning off the build up of material on exterior surfaces has become very widespread particularly since water is not harmful to the environment. Some examples of surfaces which are easily cleaned with a high pressure water spray are: the bottom of a ship where marine growth accumulates, the walls of a paint booth were coats of paint build up, and the exterior of an engine block where grease, grit and grime build up.
A typical high pressure water spraying system includes an internal combustion engine, a pump driven by the engine, a source of water connected to the pump and a spray nozzle assembly connected by a high pressure conduit to the output of the pump.
In many such systems, the nozzle assembly includes a nozzle with a small orifice and a trigger operated dump valve for dumping water from the nozzle assembly when the trigger is released. Of course, when the trigger is depressed the pressurized water flows to the nozzle and out the orifice. The pressure of the water can be controlled by pre-setting the engine throttle or, alternatively, the engine throttle can be remotely controlled by means of an electric switch on the nozzle assembly.
Dumping of water at the place where the spray cleaning is being done is often inconvenient, ackward and messy. Also, it is tedious and tiring for the operator to hold a trigger depressed for an extended period of time against a significant spring pressure of a biasing spring in a conventional dump valve.
As a result, it has been proposed to provide some sort of relief at or near the pump, or recirculation through the pump, of pressurized liquid in a liquid spraying system such as in a high pressure water cleaning system. Also it has been proposed to have a remote control for the relief or recirculation. Examples of liquid spraying systems having some sort of relief or recirculation at or near the pump are disclosed in:
U.S. Pat. Nos. 1,280,477; 3,433,415; 3,827,827.
As will be described in detail hereinafter the control system of the present invention differs from the previously proposed systems by not only eliminating dumping of liquid at the place where cleaning is being done by dumping at the pump, but also by providing for cushioning of the discharge of the pressurized liquid being dumped and by providing for remote control of both dumping and engine acceleration with a single, easily movable trigger mounted on the nozzle assembly of the spraying system.